EOS is a similar cryptocurrency to ETH but excels in areas ETH fails. EOS specializes in scalability, an area where ETH suffers greatly. However, ETH has attained the most important thing of all market penetration. The overwhelming majority of ICOs from the past year were ETH based on the ERC-20 platform. This sheer quantity led to many scaling problems for ETH and this is specifically where EOS excels. So, It's better to invest in both EOS as well as ETH in my opinion.